In a gas turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases. The hot gases are channeled through various stages of a turbine which extract energy therefrom for powering the compressor and producing work. The turbine stages often include stationary metal turbine nozzles having a row of vanes that channel the hot combustion gases into a corresponding row of rotor blades. Over time, the heat generated in the combustion process can rapidly wear the turbine vanes and blades, thereby reducing their usable life. This wear can be especially pronounced at the thin trailing edge of an airfoil.
In some engines, the turbine vanes and turbine blades both have corresponding hollow airfoils that can receive cooling air. Cooling air can be directed through the airfoils before being exhausted through one or more slots near an airfoil's trailing edge. Often, the cooling air is compressor discharge air that is diverted from the combustion process. Although diverting air from the combustion process helps prevent damage to the turbine airfoils, it can decrease the amount of air available for combustion, thus decreasing the overall efficiency of the engine.
Aerodynamic and cooling performance of the trailing edge cooling slots can be related to the specific configuration of the cooling slots and the intervening partitions. The flow area of the cooling slots regulates the flow of cooling air discharged through the cooling slots, and the geometry of the cooling slots affects cooling performance thereof. For instance, the divergence or diffusion angle of a cooling slot can affect undesirable flow separation of the discharged cooling air that would degrade performance and cooling effectiveness of the discharged air. This might also increase losses that impact turbine efficiency.
Notwithstanding, the small size of the outlet lands and the cooling performance of the trailing edge cooling slots, the thin trailing edges of turbine airfoils oftentimes limit the life of those airfoils due to the high operating temperature thereof in the hostile environment of a gas turbine engine.
Accordingly, it is desired to provide an airfoil having improved durability and engine performance. It is also desired to minimize the amount of cooling flow used for trailing edge cooling and maximize fuel efficiency of the gas turbine engine.